/*
基本类型：Number,String,Boolean,null undefined
复杂类型：Array,Object,Function
*/
// 联合类型  类型1 | 类型2

// type:类型别名  type 变量名 = 类型
type NS = number | string
type XN = number
const aaa: XN = 999
let xxx: NS = 10
xxx = 'hello'
const arr: NS[] = [1, 2, 3]
arr[0] = 'hello'

export {}
